1. Technical Field
The present invention relates to a heat exchanging mechanism of a cylinder of a screw type extruder and a heat exchanging method.
2. Description of Related Art
A cylinder of an extruder is cooled or heated by passing a medium through a cooling/heating jacket provided in the cylinder to exchange heat using evaporative latent heat or sensible heat of the medium.
A medium jacket is provided on the outer circumference of a screw receiving hole for receiving a screw in a spiral shape (JP-A-11-198215 and JP-A-5-057768) or is provided in the axial direction of a screw receiving hole as shown in FIGS. 5A to 7B.
FIGS. 5A to 7B are front views and side views of an intermediate cylinder, a vent cylinder and a side feed cylinder of a twin-screw extruder including a conventional heat exchanging mechanism, respectively, each of which A is the front view and B is the side view.
In the intermediate cylinder 110 shown in FIG. 5A, a screw receiving portion 100 having a cross-sectional shape in which two circular arcs communicate with each other and a drill jacket 101 surrounding the screw receiving portion are formed. Tie bar bolt holes 103 are formed in the outside of the drill jacket 101.
The drill jacket 101 is used as a cooling/heating jacket and includes drill holes 106 which are a plurality of through-holes formed in an axial longitudinal direction of the screw receiving portion 100 and have a circumferential shape, a medium flowing port 104 which communicates with the outside of the cylinder, bypasses 105 for communicating the drill holes 106 with one another, and jacket closing plates 107 for forming a medium flow path, that is, the jacket, by closing the both ends of the drill holes 106 and the bypasses 105 in the front and rear surfaces of the intermediate cylinder 110. The jacket closing plates 107 are attached to the both ends of the intermediate cylinder 110 by welding. (see FIGS. 5A and 5B)
A vent hole 121 is formed in a vent cylinder 120 shown in FIGS. 6A and 6B and a side feed hole 131 is formed in a side feed cylinder 130 shown in FIGS. 7A and 7B. Accordingly, in the cylinders 120 and 130, the drill holes 106 are formed in a region in which the vent hole 121 and the side feed hole 131 are not formed.
Next, the flow of the medium in the drill jacket 101 will be described. The medium is fed from one side of the flowing port 104. The fed medium flows into the bypass 105 in the circumferential direction of the screw receiving portion 100 and then flows into the drill hole 106 through one end of the drill hole 106 which communicates with the bypass 105. The medium flowing into the drill hole 106 flows to the other end of the drill hole 106 in the axial direction of the screw receiving portion 100 while the inside of the screw receiving portion 100 is cooled or heated. The medium which reaches the other end of the drill hole 106 flows into an adjacent drill hole 106 through the bypass 105. The medium continuously flows as described above and finally flows out of the intermediate cylinder 110 through the other side of the flowing port 104.
A method of flowing the medium in the drill jacket 101 of the vent cylinder 120 shown in FIGS. 6A, 6B or the side feed cylinder 130 shown in FIGS. 7A, 7B is similar to the above-described method of flowing the medium in the drill jacket 101 of the intermediate cylinder 110.